The scary slasher-movie genre has been ratcheted up several notches with the release today of "Halloween: H20."

Jamie Lee Curtis brings a lot of baggage from the original "Halloween," in which she made her movie debut in 1978, and that's entirely to this sequel's benefit.

Just as valuable is the concept of the role she plays, which has been elevated to the mythological level of avenging Fury. "Halloween: H20" is not a routine cut-and-paste horror but a full-fledged revenge fantasy -- and a completely satisfying one. The audience keeps buzzing for minutes after it's over.

The thriller, directed by Steve Miner, is steeped in theatrical know- how -- including a genuine anticlimax, but it would be dirty pool to reveal any details. Like "The Terminator," this one keeps coming back atcha.

The movie with the pi-sign title may have the summer season's worst title, but "Halloween: H20" has the best because it's not what you think. It has nothing to do with water, although Curtis has said she wanted the advertising tag line to be, "Blood is thicker than water." The title is shorthand for "Halloween," 20 years later.

Curtis for all intents and purposes is still Laurie Strode, sister of serial killer Michael Myers, but in the 20 years since he went off the deep end watching their sister have sex, she has undergone a name change, had a baby, moved to Northern California (doesn't everybody?) and become headmistress of a posh private secondary school. She is, in addition, a mess.

Alcoholic, drug addicted, not very together as a parent and squirrelly as a result of the trauma 20 years ago, she is at least not paranoid. Her killer brother really is out to get her.

"H20" may even be better than John Carpenter's original, and that's going some, because it capitalizes on the Laurie Strode character's history. It makes her much more complicated and even archetypal. Plus, it's fun.

It even has a classic recognition scene, when the hero comes to understand her fate and accepts it -- the Greeks knew what they were

doing, theaterwise. Laurie, now known as Keri Tate, has an opportunity to escape her nemesis but turns back to track him down instead.

Slasher films often seem merely a joke, and with good reason, but in this case that's too bad. Curtis, with her plain, unglamorous appearance, rises to the occasion and delivers as compelling a performance as any this summer.

"H20" begins with one self-contained horror sequence set in adjoining houses in Indiana, to establish that Michael Myers has escaped from custody and knows where Lau rie lives. There is another sequence in a roadside rest area to show that the white-faced killer mime (well, he never speaks, does he?) is on his way to California.

The interest in the rest of the first hour of the film, when there are many false shock cuts, lies in guessing which of the characters is going to get it.

"H20" is clearly intended to capitalize on the success of "Scream" and similarly draws many of its supporting cast from television. Josh Harnett, who plays Keri's 17-year- old son, was in the short-lived Robert Pastorelli series "Cracker," and it's fair to wonder whether that will be his fate here, too. One character who is too warm and fuzzy to live is the boyfriend of Laurie/Keri, played by Adam Arkin ("Chicago Hope"). LL Cool J shows up as a gatekeeper at the school, and the teenage students include Michelle Williams ("Dawson's Creek"), the beaky Adam Hann-Byrd ("NYPD Blue") and Jodi Lyn O'Keefe ("Nash Bridges").

The one I was really hoping would get it is Janet Leigh, who has a cute (ugh) cameo with her daughter Jamie Lee and telegraphs "Psycho," "Psycho," "Psycho" to us. She even gets into the very same automobile she drove to the Bates Motel in the Hitchcock classic, and for that alone deserves to die.